1. Field of the Invention
The present invention relates to an uninterruptible power supply, in particular, to a 115 V or 230 V AC output selectable, power saving, uninterruptible power supply.
2. Description of the Prior Art
As disclosed in FIG. 1, a conventional uninterruptible power supply system has an uninterruptible power system and a switching power supply integrated into one unit, wherein a battery power source is converted into an AC power source to supply, a computer monitor display and the like. However, owing to a linear transformer is employed for a direct boost convertion, this type of an uninterruptible power supply is large and heavy, such that it is not readily installed in a mini-size power supply. In particular, the AC output has no stable voltage and is unable to be switched into a 115 V or 230 V backup power source. As a result, two separate circuits are required. Therefore, the conventional uninterruptible power supply has an advantage of simple circuitry, but has disadvantages of big in size, heavy in weight and not capable of selecting a 115 V or 230 V AC output.